Process for the preparation of technically pure anthracene and carbazole from crude anthracene



p 1956 F. P. K. DE JONG 2,764,595

PROCESS FOR THE PREPARATION OF TECHNICALLY PURE ANTHRACENE AND CARBAZOLEFROM CRUDE ANTHRACENE Filed May 13, 1953 3 Sheets-Sheet 1 Tel. 1-: D

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ATTORNEYS.

Sept. 25, 1-956 F. P. K. DE JONG 2,

PROCESS FOR THE PREPARATION OF TECHNICALLY PURE ANTHRACENE AND CARBAZOLEFRQM CRUDE ANTHRACENE Filed May 15, 1955 3 Sheets-Sheet Z FIGZ Carb.

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ATTORNEYS.

p 1956 F. P. K. DE JONG 2,764,595

PROCESS FOR THE PREPARATION OF TECHNICALLY PURE ANTHRACENE AND CARBAZOLEFROM CRUDE ANTHRACENE Filed May 13, 1953 3 SheetsSheet 3 /N VE N TORan-s- P. KaeJon y,

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PROCESS FOR THE PREPARATION OF TECHNI- CALLY PURE ANTHRACENE ANDCARBAZOLE FROM CRUDE ANTHRACENE Frans P. K. De Jong, Geleen,Netherlands, assignor to Stamicarbon N. V., Heerlen, NetherlandsApplication May 13, 1953, Serial No. 354,698

3 Claims. (Cl. 260-318) My invention relates to a process for thepreparation of technically pure anthracene and carbazole from crudeanthracene obtained by crystallisation and separation from theanthracene oil fraction in tar distillation. The product obtained from.anthracene oil by cooling and centrifuging contains about 25% ofanthracene, 25% of carbazole, 38% of phenanthrene and of oil and otherconstituents. By recrystallisation from naphthalene oil this product maybe worked up into a substance containing 40% of anthracene, 38% ofcarbazole, 12% of phenanthrene and 10% of oil and other constituents.

In the production of anthracene andc-arbazole from the crude productsuse is often-made of the difference in solubility of these substances invarious solvents. The employment of pyridine and fura'n derivatives isalready known and it has also been proposed to prepare technically pureanthracene from the crude crystallised prodnot from naphthalene oil, byextracting it successively with toluene and acetone. Phenanthr-ene, oiland further admixtures are for the greater part removed by toluene.Carbazole dissolves in acetone. The residue of the extraction isanthracene with a purity of about 97%. From the acetone extract amixture of carbazole and anthracene can be recovered which containsabout 60 to 75 of carbazole.

It is the main object of my invention to provide a process of the kindspecified by which both anthraceiie and carbazole are recovered asproducts with a purity of over 95%. A further object of my invention istoiprovide a simple cyclic process by which the said'pure products areobtained in a continuous manner.

'Further objects of my invention will appear hereinafter and in theclaims hereof. According to my in'vention, technically \pure anthraceneand carbazole are prepared from crude anthracene by a process whichcomprises the following essential steps: (a) treating the crude productfirst with sufiicient toluene only m fextract substantially all thephenanthrene and associated imstep (a); (f) collecting technically pureanthracene from the residue left in step (b); (g) collecting technicallpure carbazole from the residue left in step (d). w

The residue of the extraction of crude anthracene with toluene andacetone is anthracene with a purity of 96 to 98%, the residue of thesecond toluene extraction being carbazole with a purity of 96 to 99%.Phenanthrene, oil and other admixtures are discharged into thetolueneextract of the first stage and recovered therefiroin'by, distilling thetoluene, if desired.

By using, according .to my invention, the same solvent for thepurification of carbazole as -was used for the first treatment of thecrude anthracene, a number of extra advantages are obtained. The extractof the crude 2,764,595 Patented Sept. 25, 1956 carbazole containscomparatively rather large amounts of carbazole and anthracene. Theseamounts are now reintroduced into the process in a simple manner. At thesame time other impurities in the carbazole which are soluble in tolueneare recycled to the first stage, so that these impurities may be removedtogether with the crude phen'anthrene which has only little value as itis. For the further processing of the crude phenanthrene to produce e.g., carbon black these impurities do not cause hindrance.

A second advantage of the application of toluene, acetone and toluenesuccessively as solvents is that it is not necessary to remove thetoluene completely from the residue of the first stage, for lowpercentages of toluene do not perceptibly interfere with the acetoneextraction. After removal of the acetone from the acetone extract bydistillation, this toluene is left in the precipitated crude carb'azoleand is received in the toluene which is to be added for the tolueneextraction of this carbazole. By preference the distillation of theacetone out of the acetone extract is carried out with addition oftoluene, which may be heated if desired, :as a result of which theformation of crusts is avoided.

The process of my invention makes it possible to avoid technicallycomplicated filtering or centrifuging and subsequent drying processesduring the extraction, while still leaving it possible to avoidaccumulation of impurities during the process or an undesired mixing ofsolvents. Only in the separation of the final products, anthracene andcarbazole, is it necessary to use a centrifuge and a drier.

My invention will nowbe explained with the help of the accompanyingdrawings showing flow sheets illustrating different ways of carrying outthe invention.

*Figure 1 gives a simple flow sheet for working up anthracene. The crudeanthracene is extracted with toluene in a first treatment 1. Thistreatment may be continuous or be carried out in a number of stages incountercurrent; The resulting extract is distilled in a treatment 6, inwhich, besides toluene, a mixture of phenanthrene, oil and otheradmixtures is obtained. This mixture may, e. g., be further processed toproduce carbon black. The residue of the extraction process '1 issubsequently, likewise continuously or in a number of stages incountercurrent extracted with acetone 2. After drying the residue isanwthracene with a purity of over 96%. Subsequently the acetone isdistilled out of the acetone extract 3 and the resulting solid product,consisting of crude carbazole with a rather high content of anthraceneis extracted with toluene 4. p

The residue of this extraction, after it has been dried, is carbazolewith a purity of over 97%. A large. part of the toluene is distilled 5out of the extract, which consists of toluene in which mainly anthraceneand carbazole are dissolved, while the rest is introduced into the firststage of the extraction 1. This distillation is'necessary because in thesecond extraction with toluene 4 much larger amounts of liquid have tobe used than in the first extraction 1. In the first extraction 1, theimpurities are removed as completely as possible with as small aspossible an amount of "liquid, for, the carbazole and anthra-' cenedissolved in this liquid are removed and thus lost. In practice it hasbeen found possible to keep these losses below 10% without using a morecomplicated separation system.

Figure 2 gives a more elaborated flow sheet.

The crude anthracene is, in this way of carrying out the invention,-extracted with toluene in two stages and with acetone in two stages.-

The first extraction 11 is carried out with the toluene extract of theextraction stage 13, to which moreover the partly distilled tolueneextract of extraction stage 19 has is avoided. .column a sharpseparation between acetone and toluene ments 12 to 17 may all take placein the same apparatus. This may consist, e. g., of a closed vessel,which in add1- tion to the necessary feedconduits, is providedwith astirring device, a discharge aperture through which the contents may beremoved rapidly and a discharge aperture provided with a screeningdevice in such a way that only the liquid is allowed to flow off. For,it has been found that it is not necessary in this extraction process instages for the residue to be completely freed of solvent between thevarious stages. The draining of the residue appears to be sufficient,even when one passes from toluene as the solvent to acetone as thesolvent. For, it

appears that slight quantities'of toluene cause no percepftibledisturbance in the extraction with acetone.

The extract which in the separating treatment 12 is vseparated'from theresidue contains phenanthrene, oil and other impurities in aconcentrated form. By a distillation process 23 the toluene isrecovered. The residue 1s again extracted with fresh toluene 13. Thesolvent is separated from the residue 14 and recycled to the firstextraction stage 11. Subsequently the residue is ex- .tracted with theacetone extract of the extraction stage 17 in which process 15 freshacetone is supplied, if necessary, latter which an extraction with freshacetone is carried out .sulting crude carbazole is subsequentlyextracted with toluene 21, centrifuged out 22 and dried 26. The finalproduct consists of carbazole with a purity of over 97%.

The liquid from the centrifuge 22 is used, as before stated, .in thedistillation of stage 19. The liquid obtained in the separation whichcontains rather large amounts of anthracene and carbazole, is partiallyconcentrated by evaporabeen added. The extraction 11 and the followingtreattion .25 and subsequently added to thefirst extraction stage 11.

The addition of toluene to the distilling liquid in treat- ,menttl9 hasthe advantage that in this way the formation of crusts and crystalmasses which are difficult to process It has been found that even with asimple can be obtained.

Sometimes it may be advantageous to cool the mixture between treatments19 and 20 so that less carbazole is circulating. However, the factshould then be borne in mind that too much anthracene can crystallizeout in i the form of mixed crystals with carbazole.

Figure 3, finally, gives a flow sheet according to which extraction alsotakes place in several stages. However, in this case the firstextraction process is combined with the concentration by evaporation ofthe toluene extract' from the crude carbazole. For, in treatment 31crude anthracene is added to a distilling mixture of this tolueneextract (originating from treatments 42-43) and a toluene extract from asubsequent extraction 34 of the crude anthracene. The resulting mixtureis concentrated by evaporation, until an amount of liquid is left, equalto about 2 to 3 times the amount of anthracene added. Thereafter, thewhole is cooled 32 and separated 33. By distillation 47 the extract isseparated into toluene and a liquid mixture of phenanthrene, oil andother impurities.

The crude anthracene is subsequently extracted with fresh toluene in twostages 34 and 36 in countercurrent. The extract is passed on todistillation stage 31. Then the residue is extracted with acetone in twostages 38 and 40 in counter-current, centrifuged off 41 and dried 48,which treatments finally result in the formation of anthracene with apurity of over 96%.

Subsequently the acetone extract is distilled 42 with addition of liquidfrom treatment 46, which liquid consists mainly of toluene, theresulting toluene extract is introduced into the first distillationstage 31, the residue is treated with toluene 44, and the resultingmixture is cooled 45 and centrifuged 46. After drying 49 the solidsubstance consists of carbazole with a purity of at least 97%.

When the operation was carried out according to the flow sheet down inFigure 3, 40 kg. of anthracene (purity 97%) and 35 kg. of carbazole(purity 97.5%) were obtained per 100 kg. of crude anthracene(composition: 44% of anthracene, 37% of carbazole, remainderphenanthrene, oil, etc.), 25 kg. of a mixture consisting for aconsiderable part of phenanthrene being removed. 20 kg. of toluene and10 kg. of acetone were lost in the process, mainly in the driers.

In operation 31, 400 kg. of toluene extract obtained in treatment 42 and100 kg. obtained in treatments 34 to 36 were added per 100 kg. ofmixture, 300 litres of toluene being distilled off.

In the subsequent extraction stages 34 and 36 the starting material wastoluene, of which an amount of litres was used. Per 100 kg. of crudeanthracene about 800 litres of acetone were in circulation. 400 litreswere used'for the extraction of the second stage 40. For the extractionof the crude carbazole (treatments 42 to 46) use was made of about 400litres of toluene per 100 kg. of crude anthracene.

The whole extraction may, as much as possible, be carried out at roomtemperature. If the operation is carried out at a higher temperature theextraction may be performed more rapidly and with the use of smalleramounts of solvent.

The extraction is preferably carried out with constant stirring.

I claim:

1. In a process for the manufacture of technically pure anthracene andcarbazole from crude mixtures, containing anthracene, carbazole andphenanthrene as the principal constituents, wherein said crude mixtureis first treated with toluene to extract phenanthrene, the resultingresidue is next treated with acetone to extract a solution of carbazolefrom said residue and technically pure anthracene is collected as aresidue from said acetone treatment, the improvement which comprisesdistilling said acetone from said solution of carbazole and subjectingthe raw carbazole obtained thereby as a distillation residue to anextraction treatment with toluene and separating technically purecarbazole crystals from the toluene solution thus obtained.

2. The process of claim 1 wherein part of the toluene in the finaltoluene solution is removed by distillation and theremainder of thesolution is added to said crude mixture.

3. The process of claim 1 wherein toluene is added to said solution ofcarbazole in acetone .prior to said distillation whereby thedistillation residue resulting therefrom comprises amixture containingcarbazole and toluene, and whereby the formation of incrustations isavoided and saidacetone is rapidly removed.-

References Cited in the file of this patent UNITED STATES PATENTS1,879,090 Cislak Sept. 27, 1932 2,622,087 De Bruijn Dec. 16, 19522,675,345 Andrews Apr. 13, 1954 FOREIGN PATENTS j g 7,868 Great BritainJuly 8, 1899

1. IN A PROCESS FOR THE MANUFACTURE OF TECHNICALLY PURE ANTHRCENE ANDCARBAZOLE FROM CRUDE MIXTURES, CONTAINING ANTHRACENE, CARBAZOLE ANDPHENANTHRENE AS THE PRINCIPAL CONSTITUENTS, WHEREIN SAID CRUDE MIXTUREIS FIRST TREATED WITH TOLUENE TO EXTRACT PHENANTHRENE, THE RESULTINGRESIDUE IS NEXT TREATED WITH ACETONE TO EXTRACT A SOLUTION OF CARBAZOLEFROM SAID RESIDUE AND TECHNICALLY PURE ANTHRACENE IS COLLECTED AS ARESIDUE FROM SAID ACETONE TREATMENT, THE IMPROVEMENT WHICH COMPRISESDISTILLING SAID ACETONE FROM SAID SOLUTION OF CARBAZOLE AND SUBJECTINTHE RAW CARBAZOLE OBTAINED THEREBY AS A DISTILLATION RESIDUE TO ANEXTRACTION TREATMENT WITH TOLUENE AND SEPARATING TECHNICALLY PURECARBAZOLE CRYSTALS FROM THE TOLUENE SOLUTION THUS OBTAINED.